The Amazon River, the basin of which covers a land area the size of the continental United States, is an amazingly biodiverse area. It is home to 60 percent of the world’s rain forests, and it plays an important role in regulating the climate of South America — and North America. It is believed to be about 4,000 miles long. Remoteness has protected it from human encroachment, but that situation is rapidly changing. As many as 60 dams are planned for Brazilian sections of the Amazon alone. These projects would displace indigenous people and flood national parks.